De or het conditioning?

The correct Dutch article is:

de conditioning

Rule Words ending in -ing: almost always de. See the rule
Meaning (Dutch) klimaat-, temperatuurregeling, luchtbehandeling

How to use conditioning

the conditioningde conditioning
this conditioningdeze conditioning
that conditioningdie conditioning
our conditioningonze conditioning
your conditioningjouw conditioning
every conditioningelke conditioning
which conditioning?welke conditioning?
a big conditioning / the big conditioningeen grote conditioning, de grote conditioning

Dutch words ending in conditioning

airconditioning

In compound words, the last part decides the article. See the rule

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).